Refinery blowdown and relief system



May 14, 1957 E. STRUNK REFINEIRY BLOWDOWN AND RELIEF SYSTEM 3Sheets-Sheet 1 Filed Feb. 25. 1952 FIG.

VENT STACK CONDENSED HYDROCARBON Al M 5 A 4 L F T k NU O ES T RS 4 mam w4 WPC H D l 2 4 Q ,L m

7 2 a m 6 F 2 F 3 2 HI, Ml h I 1 N 4 W 0M 2 DU R fl B L UNIT RELIEF UNITUNIT RELIEF RELIEF INVENTORL E DWARD STRUNK A TTORNEYS y 4, 1957 E.STRUNK 2,792,070

REFINEIRY BLOWDOWN AND RELIEF SYSTEM Filed Feb. 25, 1952 3 Sheets-Sheet2 EIIEIL' STEAM G 50 k8? I '1'. I F/ STEAM I 54 l I WATER 55 53 WATER 48I T0 FLARE I I I I I J ;47 l 1 l 5| IL RELIEF LINE 2 I 1 LIQUIDHYDROCARBON I 49 WATER ;i- TO FLARE INVENTOR. EDWARD STRUNK A T TORNEYSMay 14, 1957 E. STRUNK 2,792,070

REFINERY' BLOWDOWN AND RELIEF SYSTEM Filed Feb. 25, 1952 3 Sheets-Sheet3 FIG. 4. 5:

i /82 27 ]i r i 1 l l 83 1 23 INVEN TOR.

EDWARD STRUNK BY REFINERY BLUWDUWN RELEF SYSTEM Edward Strunk, Sweeny,Tom, assignor to Phillips Ferroleum Company, a corporation of DelawareApplication February 25, 1952, Serial No. 273,308

14 Claims. (Cl. 183-4) This invention relates to refinery blowdown andrelief systems. In a further aspect this invention relates to systemswhereby gases may be released to the atmosphere under controlledconditions. in a further aspect this invention relates to a relief orblowdown system in which a flare is used in connection with a ventstack. in a further aspect this invention relates to a system in which aflare is used to dispose of normal amounts of relief gases and anormally sealed vent is provided to dispose of excessive amounts ofthese gases.

It is common practice in refineries to collect hydrocarbon relief andblowdown gases and to pipe them to a flare. Such a flare must be locateda considerable distance from the processing area because of the firehazard. An alternative which has been used is to provide a vent stackextending high in the air in the processing area. The first method isexpensive for, to be eifective, the flare line must be of large capacityto avoid restricting the flow and imposing that pressure on other reliefvalves in the system which would prevent their opening at the setpressure, but it has the advantage of giving visible and immediateevidence of loss whether through leaking or inadvertently openedblowdown valves, since the height of the flame gives a rough indicationof the amount of gas being burned. The second alternative is lessexpensive in that an adequately sized line can be installed over therelatively short distances required; however, it has the disadvantagesof giving no indication of when or how much loss to blowdown occurs andwill create a fire hazard unless the gases are properly dissipated. Whenthe gases to be dissipated are heavier than air, it is necessary tosupply steam to this stack so that the gas leaving the stack will belighter than air.

I have invented a system which provides a method of combining theadvantages and eliminating the disadvantages of both systems. Itconsists of installing a gas blowdown or relief header system tied to alarge vent stack in the still area, putting a water seal in the path ofsaid gases to the vent stack which will open in case of excessive flowof blowdown material, and piping relatively smaller, normal quantitiesthrough a smaller capacity line to a remotely located flare. The flareindicates by the size of the flame the magnitude of the smaller, normalgas losses. An indicator showing when the water seal is blown givesevidence of large loss.

By the various aspects of this invention, one or more of the followingobjects will be obtained.

An object of this invention is to provide an improved refinery relief orblowdown system. A further object is to provide an improved systemwherein relatively small amounts of gases are burned by a remotelylocated flare and excessive amounts of such gases are vented by means ofa vent stack. A further object of this invention is to provide animproved method of providing for the safe release of gases to theatmosphere. A further object of this invention is to provide a method ofventing gases from a refinery system which comprises flaring relativelysmall atelnt' "cc V 2,792,0170 Patented May 14, 1957 amounts of saidgases in a remotely located flare and venting large amounts of saidgases through a vent stack. A further object of this invention is toprovide an improved water seal for use with the vent stack of myinvention.

Other objects and advantages of this invention will be apparent to thoseskilled in the art.

Accompanying and a part of this invention is a drawing in which:

Figure 1 is a diagrammatic view of a refinery relief and blowdownsystem;

Figures 2 and 3 are modifications of the system of this invention; and VFigure 4 is an enlarged cross section View of the water seal shown inFigure l.

Referring to the drawings and to Figure 1 in particular, iii representsa blowdown drum containing bubble or water wash trays 11. Gaseous reliefheader 12, located at a convenient place in the plant is connected tounit relief lines 13, 14, and 16 and also to the lower portion of drum10 by means of conduit 17. Extending from the top of drum 10 is ventstack 18 which is provided with steam distributor 19, said steamdistributor being connected to steam line 21. A water seal is providedin the upper end of drum 10 which comprises a flat annular member 22, atubular member 23 positioned in the hole of said annular member, adownflow conduit 24, and a cap 26. The height of the member 23 should beslightly above the height of the downflow conduit 24, and the sides 27of cap 26. extend to a point below the inlet opening of conduit 24.

In Figure l, cooling water is circulated over the water seal and thetrays 11 by means of conduits 28, 29, and 31. Connected to this systemis makeup water supply conduit 3% Pump 32 is located in this system toforce the water to the top of the column. In the return line to the topof the column there is provided cooler 33 with bypass 34, valves 36 and37 regulating the flow therethrough. While I have shown manual controlvalves at this point it will be evident that a temperature control couldbe utilized to by-pass cooler 33 as long as the water is cool enough.Conduit 38 extends from the lower portion of drum 10, condensedhydrocarbons being removed therethrough.

Difierential pressure control 39 is provided with one side 41 connectedjust above plate 22 and the other side 42 connected below the waterseal. This pressure control 39 serves to operate valve 43 in line 21.Below the water seal there is provided conduit 44 which conveys gas to aflare (not shown). A meter 45 is provided to indicate the amount of gasflowing through conduit 44.

in Figure 2, a modification of my invention is shown wherein the drum isdesignated 46. In this modification separate sources of liquid are usedfor the condensing column and the water seal. The contacting or waterwash trays in the column are designated 47, the water inlet 48, and thewater outlet 49. Input conduit 51 communicates with the lower portion ofdrum 46. Hydrocarbon removal conduits comprise conduit 52 for condensedproducts, conduit 53 for normal gaseous flow and vent stack 54 for largegaseous release. The lower end of vent stack 54 extends into container55 which, in operation, has a liquid level maintained therein. A line 56in stack 54 allows water which is blown into stack 54 when the waterseal is broken to flow back to the bottom of 46. Conduit 57 can be usedto supply this liquid. In the upper portion of vent stack 54 there isprovided steam distributor 58 which is connected to conduit 59. In thismodification, I have shown flow meter 60 as the steam inlet operatingmeans. This meter is of a type that does not restrict gas flow such asPitot tube and is not used to quantitatively meter the gas flow but isoperatively connected to open the steam valve in response to a positiveflow of gas up the stack. Valve 61 is provided in conduit 48, this valvebeing controlled by means of a temperature responsive device 63 which isactuated by the temperature in line 51.

The simplest form of my invention is illustrated in Figure 3 wherein thedrum is designated 66. Relief conduit 67 communicates with one end ofthis drum. At the other end of the drum there are provided conduits 68extending to the flare and 69 to convey liquids from the drum. In thismodification vent stack 71 extends into container 72 which is providedwith liquid supply conduit 73 and liquid overflow 74. Extending fromvent stack 71 is liquid removal conduit,76.

In Figure 4 there is shown an enlarged view of the upper section ofdrum. 10 as shown in Figure 1.. This view shows the details ofconstruction and illustrates a case in which two downflow conduits 24are provided. A manhole 81, is shown in the upper part of cap 26, saidcap being supported above the tubular member 23 by means of supports 82.Connections for attachment of differential pressure control 39 are shownat 83 and 84.

The operation of the system of this invention is as follows, this systembeing readily adaptable to any size installation. Referring to Figure l,the relief lines from various parts of apparatus are all tied intorelief header 12 and the gases flow from this header, through conduit 17to the blowdown drum 10. In drum 10 the gases are contacted with waterand relatively higher boiling hydrocarbons are condensed and removedthrough line 38. This cooling water is removed through conduit 28 andrecirculated to the top of the column. Conduits 28 and 38 are normallyprovided with liquid level controls (not shown) but this removal can bemanually controlled. The water seal in the upper part of the drum is ofsufficient size that all of the gases from normal leakage in the plantwill flow through conduit 44 to the flare. The wash water for thiscolumn normally fills the space between the cap 26 with its sides 27 andthe tubular section 23 connected to the annular ring 22. Water which issupplied flows through conduit 24 down into the column and gases areprevented from flowing upwardly therethrough by means of the seal orwell on the lower end of this conduit.

When the water wash is circulated in this column it may be necessary tocool this water and this is done by means of heat exchanger 33. If largeamounts of fresh water are supplied, this cooling is generallyunnecessary.

When a relief valve on some apparatus blows, a large surge of gas flowsinto the drum 10. When the pressure in drum 10 caused by the increasedgas flow exceeds an amount determined by height of the water seal, thegases blow the water seal and vent to the atmosphere through stack 18.When this water seal is broken, differential pressure control 39 isactuated and this serves to operate valve 43 causing dispersant steam tobe released from distributor 19. This steam lowers the specific gravityof the gases being vented so that they are dispersed and do not settlearound the apparatus causing a fire hazard. As soon as the excess flowis reduced, the water will again establish a seal on the stack, thesteam will be shut off, and normal conditions will result. The flarenormally burns continuously so that the magnitude of loss will bevisible at all times. In addition to the flare, a meter 45 may beinstalled in conduit 44 to indicate the magnitude of gases flared.

The modification of Figure 2 operates in a slightly different manner. Inthis case there is no steady water wash and the water seal is normallynothing more than the static water head in container 56, this waterbeing supplied by conduit 57. Normal amounts of relief gases passdirectly from conduit 51, through drum 46, and to the flare throughconduit 53. Water and liquid hydrocarbons are removed from the lowerpart of the drum. When gases entering 46 through line 51 exceed apredetermined temperaturevalve 61 is opened in responseto temperatureresponsive device 62, resulting in condensation of condensable elementsin the relief gases. When a relief valve blows the increased flow causesthe water seal to blow and the gases are vented through vent stack 54 tothe atmosphere. Steam is added to this vent stack by means ofdistributor 58.

After the situation has been returned to normal the container 55 isagain filled with water and is again in readiness for operation.

In some installations surplus steam may be continuously vented toatmosphere by means of line 50 and this will result in some condensationin vent stack 54 which serves to maintain the liquid in the water sealcontainer 55. In other installations a small flow of water iscontinuously supplied to container 55. In such installations I havefound it desirable to use an overflow conduit which connects the stackwith the lower part of drum 46. The steam line 59 serves to supply steamfor the purpose of the above-mentioned dispersing effect and also forextinguishing any fire which might be started by lightning.

In Figure 3 a very simple form of this invention is illustrated whereina drum 66 is similar to the usual knockout drum in which liquids andgases are separated. The relief gases are passed into one end of thedrum and preferably directed against the end of this drum so that mostof the liquid will be knocked out of the gas. Following this separationgaseous and liquid products are removed through conduits 68 and 6%.Conduit 68 extends to the flare and is of sufiicient size to take any ofthe normal loss of the installation. Added to this knockout drum is ventstack 71 which extends into said drum and into container 72 positionedtherein. A water level is maintained in this container which is suppliedby conduit 73. To simplify the liquid separation problem when the systemis operating normally, an overflow line 74 is provided which keepscontainer '72 from overflowing. Conduit 74 is provided with a liquidtrap seal (not shown) to prevent gases from flowing therethrougb whenthe liquid level is below the input connection to conduit 74.

Operation of this modification is quite similar to that disclosed inFigures 1 and 2 and it is not necessary to review this operationcompletely. One feature shown in connection with this modification isconduit 76 which connects the interior of conduit 71 and the interior ofdrum 66. This prevents the accumulation of excessive water head in ventstack 71 by releasing water forced into this stack to the interior ofthe drum.

Figure 4 illustrates the details of the water seal shown in Figure 1.The operation of this water seal has been described in connection withthe operation of that figure.

It should be appreciated that there are many possible variations andmodifications of this type of blowdown and relief system which will nowbecome apparent to those skilled in the art. As already pointed out,this system allows safe operation in venting small and large amounts ofinflammable gases to the atmosphere. Furthermore, this provides a systemwhich is almost entirely automatic in action and yet which is almostfoolproof as the only valve in the system is the water seal.

As many possible embodiments may be made of this invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth or shown in the accompanying drawing is to beinterpreted as illustrative and not in a limiting sense.

I claim:

1. A refinery relief system for inflammable gases comprising a blowdowndrum, a vent stack extending from the upper end portion of said drum, atleast one inlet conduit communicating with the lower portion of saiddrum, a water seal disposed in said drum between said vent stack andsaid feed conduit whereby said vent is sealed from said inlet conduit,means for condensing condcnsable hydrocarbons in said drum, a liquidbydrocarbon drawei'f conduit extending from the lower portion of. saiddrum, and means. extending from said 5, drum to a flare wherebynoncondensed hydrocarbons are conveyed to said flare.

2. The system of claim 1 wherein said vent stack is provided with asteam inlet.

3. A refinery blowdown system comprising a blowdown drum andcommunicating therewith a flare conduit and vent stack, said flareconduit being of small capacity when compared to said vent stack, atleast one inlet communicating with said drum, at least one liquidmaterial outlet extending from the lower portion of said drum, a Waterseal at the bottom of said vent stack, means operatively connected tosaid drum whereby rupture of said water seal is indicated, a steam inletconduit in said vent stack, a valve in said steam inlet conduit, and acontrol line operatively connecting said means operatively connected tosaid drum whereby rupture of said water seal is indicated and saidvalve.

4. A refinery relief system for inflammable gases comprising an uprightblowdown drum, a water seal in the upper end portion of said drum, avent stack extending from the upper end portion of said drum, water washtrays in said drum, a relief header, unit relief conduits communicatingwith said relief header, a conduit connecting said relief header and thelower end portion of said drum, a wash water inlet conduit extendinginto said drum above said water seal, a water drawoff conduit extendingfrom the lower end portion of said drum, a conduit connecting said washwater inlet and said water drawoff conduits, a pressurizer in saidconduit, a water supply conduit communicating with said wash water inletconduit, a liquid hydrocarbon drawoff conduit extending from a level insaid drum above said Water drawofit conduit, and a conduit extendingfrom a point in said drum above said Water wash trays and below saidwater seal to a flare.

5. The system of claim 4, in which a cooler is provided in said washwater inlet.

6. The system of claim 1 wherein said water seal comprises a flatannular ring positioned transversely within an upright column andconnected to said column by a gas tight seal, a tubular sectionpositioned in the hole in said annular ring and connected to said ringby a gas tight seal, at least one downflow conduit extending from alevel below the top of said tubular section to a level below saidannular ring, a well in said downflow conduit, a cap above said tubularsection having sides which extend downwardly between said tubularsection and said downflow conduit to a level intermediate the upper endof said downflow conduit and said annular ring.

7. The system of claim 4, wherein said water seal comprises a fiatannular ring positioned transversely within an upright column andconnected to said column by a gas tight seal, a tubular sectionpositioned in the hole in said annular ring and connected to said ringby a gas tight seal, at least one downflow conduit extending from alevel below the top of said tubular section to a level below saidannular ring, a well in said downflow conduit, a cap above said tubularsection having sides which extend downwardly between said tubularsection and said downflow conduit to a level intermediate the upper endof said downflow conduit and said annular ring.

8. A refinery gas relief system comprising an upright blowdown drum, aplurality of contacting trays in the mid-section of said drum, a liquidsupply conduit above said contacting trays, a relief line communicatingwith said drum, temperature responsive means in said relief line, avalve in said liquid supply conduit operatively connected to saidtemperature responsive means, at least one liquid removal conduitextending from the lower portion of said drum, a gaseous removal conduitextending from said drum at a level above said liquid removal conduit, aliquid container in said drum, a vent stack extending from a level belowthe normal liquid level within said liquid container, and a means tosupply liquid to said liquid container.

9. A refinery relief system for inflammable gases comprising a blowdowndrum, a water seal in the upper end portion of said drum, wash watertrays in said drum, an inlet conduit communicating with the lower endportion of said drum, a wash water inlet conduit extending into saiddrum above said water seal, a water drawoif conduit extending from thelower end portion of said drum, a liquid hydrocarbon drawofl conduitextending from a level in said drum above said water drawotf conduit,and a conduit extending from a point in said drum above said wash watertrays and below said water seal to a flare.

10. The method of venting gases from a refinery comprising passing saidgases to a blowdown zone, removing condensed hydrocarbons therefrom,removing to a. remotely located flare a normally flowing relativelysmall amount of said gases, removing liquids accumulating in saidblowdown zone from the lower portion of said zone, separately ventinggases in excess of said normally flowing relatively small amount ofgases from said blowdown zone in response to an increase in gas flowbeyond a predetermined amount, said latter flow being controlled by awater seal, and adding steam to said separately vented gases in anamount suflicient to lower the specific gravity of said gases, saidsteam being added downstream of said water seal.

11. The method or" claim 10 wherein the flow of said steam is controlledby a change in pressure differential upstream and downstream of saidliquid seal.

12. The method of claim 10 wherein the flow of said steam is controlledby flow of said excess vented gases.

13. The method of claim 10 wherein cooling water is supplied to saidblowdown zone to condense condensable hydrocarbons therein.

14. The method of claim 13 wherein the flow of said cooling water iscontrolled by the temperature of the gases passed to said blowdown zone.

References Cited in the file of thispatent UNITED STATES PATENTS 312,777Westinghouse Feb. 24, 1885 314,089 Westinghouse Mar.'17, 1885 1,160,689Burton Nov. 16, 1915 1,236,953 Lewis Aug. 14, 1917 1,651,051 WigginsNov. 29, 1927 1,770,221 Sweeny July 8, 1930 1,770,725 Bartels July 15,1930 1,859,670 Henderson May 24, 1932 2,274,006 Smith Feb. 24, 19422,290,065 Natho July 14, 1942 2,311,625 Bransky et al. Feb. 23, 19432,373,519 Tweit Apr. 10, 1945 2,438,619 Rattay Mar. 30, 1948 2,536,370Hughes Jan. 2, 1951 2,690,814 Reid Oct. 5, 1954

1. A REFINERY RELIEF SYSTEM FOR INFLAMMABLE GASES COMPRISING A BLOWDOWNDRUM, A VENT STACK EXTENDING FROM THE UPPER END PORTION OF SAID DRUM, ATLEAST ONE INLET CONDUIT COMMUNICATING WITH THE LOWER PORTION OF SAIDDRUM, A WATER SEAL DISPOSED IN SAID DRUM BETWEEN SAID VENT STACK ANDSAID FEED CONDUIT WHEREBY SAID VENT IS SEALED FROM SAID INLET CONDUIT,MEANS FOR CONDENSING CONDENSABLE HYDROCARBONS IN SAID DRUM, A LIQUIDHYDROCARBON DRAWOFF CONDUIT EXTENDING FROM THE LOWER PORTION OF SAIDDRUM, AND MEANS EXTENDING FROM SAID DRUM TO FLARE WHEREBY NONCONDENSEDHYDROCARBONS ARE CONVEYED TO SAID FLARE.